Bryan and Cherry Alexander / People walking down a snow slope to Windy Ridge, with altocumulus undulatus clouds above them. Patriot Hills. West Antarctica, January 2006.
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Philippe Clement / Altocumulus undulatus clouds in blue sky, Brittany, France, September 2010
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Philippe Clement / Altocumulus undulatus clouds in blue sky, Brittany, France, September 2010